1. Field of the Invention
This invention relates to a molecular beam epitaxial growth method (hereinafter referred to as MBE growth method) of compound semiconductor and apparatus of for making the same.
2. Prior arts
Molecular epitaxial growth of compound semiconductor such as GaAs, InP, or mixed crystals thereof is excellent in terms of controlling film thickness and compositions. Because of this feature, its use is gradually being adopted in the production of high-speed devices such as HEMT and optical devices such as laser diode. In the case of III-V compound semiconductors, for an example, excessive amount of Group V molecular beam is used in order to eliminate deviation from the stoichiometric composition during MBE growth, since the vapor pressure of Group V molecules is generally high. However, it is still hard to eliminate the deviation from the stoichiometric composition, as MBE is not a crystal growth under a thermal equilibrium state. While, a perfect crystal of controlled stoichiometric composition is obtained by a method called "Temperature Difference Method under Controlled Vapor Pressure" which is disclosed in, e.g., Handotai Kenkyu (Semiconductor Research) P.39 and P. 85 of Volume 23 issued by KOGYO CHOSAKAI (Industrial Research Society) in 1985. However, there is a problem in which its application to ultra-thin film growth such as the growth of super lattice is difficult.